Volume 36, Issue 3
September 1952, pages 97-134
pp 97-101 September 1952
pp 102-104 September 1952
pp 105-118 September 1952
The study of the food and feeding of the mackerel,Rastrelliger canagurta was based on the periodical examination of stomach contents of the mackerel and the plankton of the coastal waters near Calicut during the years 1949 and 1950. The relative importance of various food elements have been determined by thenumber and thepoints methods.
The mackerel has been observed to feed almost exclusively on plankton organisms. The main food constituents were copepods, cladocerans, larval and adult decapods, peridinians and diatoms. Post-larval bivalves, fish eggs and larvæ, polychæte larvæ, cirripede nauplii, appendicularians and pteropods were minor elements in the food. There was no appreciable difference between the food of the young and that of the adult mackerels.
The composition of the food varied from season to season depending upon the fluctuations in the occurrence of various planktonic elements. There was a close correlation between the food constituents and the planktonic organisms of the inshore area.
Non-edible forms like salps, medusæ, ctenophores, stomatopod larvæ, chætognaths and noctilucæ were avoided and to that extent there was selective feeding. There was feeding throughout the year although the feeding intensity varied from season to season. There was no marked period of fasting.
The feeding intensity was low during the prespawning and spawning periods and comparatively high in the 16 to 20 cm. size group. It was maximum during the period from September to December when edible plankton was abundant.
pp 119-128 September 1952
The aerobic decomposition of paddy andbajra straws by 22 fungi isolated from Allahabad soils was studied under controlled laboratory conditions. Dawson’s methods were employed with certain modifications. The decomposition was studied by determining the carbon dioxide and ammonia evolution, loss in weight and loss in total amount of carbon during a 7-day period.
The fungi were tested for their oxidase activity and out of 22 fungi only two were found to be oxidase positive.
There is no uniformity in the rates of decomposition by various fungi. In certain cases the amount of carbon dioxide evolved was more than the loss in weight and in other cases the amount of carbon dioxide evolved was less than the loss in weight of the straw. The cellulose equivalent of carbon dioxide evolved was not proportional to the loss in weight.
As a result of decomposition the change in pH of the straw was in some cases towards the acidic side and in other towards the alkaline. Further, the rate of decomposition has no relation either with change in pH of the straw or with the oxidase activity of the fungi.
There was a fair amount of correlation between the total carbon decomposed and the total loss in weight of the straw.
All the 22 fungi behaved similarly towards paddy andbajra straws.
pp 129-134 September 1952
The cankerous disease of guava (Psidium guajava L.) exhibiting characteristic spots and malformations is prevalent in Mysore. It is associated with two fungiColletotrichum psidii Curzi andPestalotia psidii Pat.
Colletotrichum psidii developed a perithecial stage in pure culture for the first time in India. The perithecia are globular, dark coloured, aparaphysate. Asci are numerous, hyaline and the ascospores are 8 in number, unicellular and granular. This stage corresponds closely toGlomerella psidii (Del.) Sheld.
Colletotrichum psidii infected the fruits of apple, chilly, lemon, papaya, plantain, mango and tomato and not brinjal and French bean.Pestalotia psidii did not infect any of these hosts. Both the fungi infected the injured fruits and leaves of guava.
Colletotrichum psidii is a general parasite whilePestalotia psidii is specialised to guava.
Three or four sprayings with 1% Bordeaux mixture or with lime sulphur solution 1:25 done at intervals of 15 days at an early stage of infection controls the spread of the fungi.